The identification of novel susceptibility genes for complex diseases like COPD could transform our understanding of disease pathophysiology and provide new pathways for treatment. We have recently collaborated in case-control genome-wide association studies that have provided compelling evidence for association of COPD susceptibility with regions on chromosome 15 (near IREB2), chromosome 4 (near HHIP), and another region on chromosome 4 (in FAM13A). However, the key genes within these GWAS loci have not been absolutely verified, and the key functional variants within these GWAS loci have not been identified. We will address several key hypotheses that will assist in the localization of functional genetic determinants within GWAS loci and investigation of their biological mechanisms: 1) African Americans and non-Hispanic Whites will share a subset of COPD genetic determinants; assessing the overlap of genetic association between these groups will localize COPD susceptibility genes; 2) Many of the functional variants influencing COPD susceptibility will regulate gene expression; and 3) Studies of Fami3a, Hhip, and /reib2 knockout mice exposed to cigarette smoke will identify the activities of these genes in COPD pathogenesis. In order to address these hypotheses and to identify potentially functional variants influencing COPD susceptibility, we will begin by localizing functional variants for COPD susceptibility in three existing GWAS loci (HHIP, FAM13A, and IREB2) using association analysis of dense SNP panels in African-American subjects from COPDGene to narrow shared COPD susceptibility regions between African-American and non-Hispanic White subjects. To localize key variants, we will assess regulatory regions around genes in these GWAS loci using chromosome conformation capture and chromatin immunoprecipitation assays. We will also assess the impact of specific variants in the regulatory region in luciferase reporter assays. We will use shRNA-mediated silencing of genes in the GWAS loci to assess whether these genes regulate the function of lung epithelial and monocyte cells lines and validate these results in primary cells. Finally, the impact of three key regional genes in GWAS loci on COPD pathogenesis will be assessed in knockout mice exposed to cigarette smoke. This project will identify the key COPD genes within GWAS loci and demonstrate the functional impact of those genes on COPD susceptibility. The multidisciplinary investigations of genetic association, genomic interactions, in vitro cell-based assays, and cigarette smokeexpose knockout mice in this project will provide important and novel insights into COPD pathogenesis.